Plants that are slightly overgrown or need some shaping may benefit from being manually pinched. Pinching is often used to increase branching, shape plants and reduce plant height. Pinching removes the apical dominance of the shoot which prevents branching. Apical dominance results from the production of auxin, a natural plant hormone by the terminal growing point and young leaves. Removing the terminal growing point and young leaves (pinching), removes the source of auxin and allows dormant buds below the pinch to grow.
Over-watered Plants: Stunted plants may be a sign of over-watering. Plants can be easily over-watered during overcast, cloudy weather, when plants with different water needs are grouped together or by an inexperienced waterer. Over-watering deprives roots of oxygen and increases susceptibility to root diseases such as Pythium and also leads to algae growth and infestations of fungus gnats and shore flies. Check roots regularly for signs of over-watering by gently removing plants from their containers.
Calibrachoas are susceptible to several diseases and nutrient disorders during production. Here is a list of common problems to watch for and prevent this growing season.
Most thrips in greenhouse are females. Adult females may live for approximately 30 to 45 days and lay from 2-10 eggs per day which are inserted into plant tissue. The first two larval stages remain protected in the tender young growth. After the 2nd instar larvae stops feeding, it migrates to the base of the plants and enters the growing medium to pupate. Adults emerge in two to five days, depending upon temperature. Thrips development occurs between 50˚F and 90˚F. They can survive cooler temperatures than 50˚F; however, there is no development at that temperature.
The bacterium Agrobacterium tumefaciens is a soil borne pathogen that causes crown gall on many types of plants. In greenhouse crops, Crown Gall has been diagnosed in recent years on mums, argyranthemum and osteospermum and this year it has been found in some of Selecta's lobelia production. Selecta found symptomatic plants in four varieties of Magadi Lobelia: Blue, Compact Dark Blue, White and Basket White. Selecta sent information out to their customers and is discontinuing shipments of Lobelia for this spring.